#pragma once is a widely supported compiler pragma, even though it is
not part of the C++ standard. Many of the issues keeping #pragma once
from being standardized (distributed filesystems, build farms, hard
links, etc.) do not apply to CMake - it is easy to build CMake on a
single machine. CMake also does not install any header files which can
be consumed by other projects (though cmCPluginAPI.h has been
deliberately omitted from this conversion in case anyone is still using
it.) Finally, #pragma once has been required to build CMake since at
least August 2017 (7f29bbe6 enabled server mode unconditionally, which
had been using #pragma once since September 2016 (b13d3e0d)). The fact
that we now require C++11 filters out old compilers, and it is unlikely
that there is a compiler which supports C++11 but does not support
#pragma once.
In commit dd8365b3f1 (Merge branch 'upstream-KWSys' into update-kwsys,
2020-04-06, v3.18.0-rc1~397^2) we imported KWSys commit `019afb6ea`
(SystemTools: Drop GetCurrentWorkingDirectory 'collapse' argument,
2020-04-03). That caused `GetCurrentWorkingDirectory` to no longer send
paths through the KWSys translation map and broke CMake's detection of
the absolute path to a build directory containing a symbolic link.
Add our own `cmSystemTools::GetCurrentWorkingDirectory` wrapper around
the KWSys method in order to restore that mapping.
Test-case-by: Ben Boeckel <ben.boeckel@kitware.com>
Issue: #16228Fixes: #20900
Provide a standardized way to handle the C++ "standard" headers
customized to be used with current CMake C++ standard constraints.
Offer under directory `cm` headers which can be used as direct
replacements of the standard ones. For example:
#include <cm/string_view>
can be used safely for CMake development in place of the `<string_view>`
standard header.
Fixes: #19491
This adds the following functions to cmStringAlgorithms:
- `cmStrToLong`: moved from `cmSystemTools::StringToLong`
- `cmStrToULong`: moved from `cmSystemTools::StringToULong`
Overloads of the given functions for `std::string` are added as well.
This adds the following functions to `cmStringAlgorithms`:
- `cmIsSpace`
- `cmTrimWhitespace` (moved from `cmSystemTools::TrimWhitespace`)
- `cmEscapeQuotes` (moved from `cmSystemTools::EscapeQuotes`)
- `cmTokenize` (moved from `cmSystemTools::tokenize` and adapted to
accept `cm::string_view`)
Changes
-------
In `cmSystemTools` this
- renames the method `ExpandList` to `ExpandLists` and makes it iterator based
and adds the methods
- `std::vector<std::string> ExpandedLists(InputIt first, InputIt last)`
- `std::vector<std::string> ExpandedListArgument(const std::string& arg,
bool emptyArgs)`
Both return the `std::vector<std::string>` instead of taking a return vector
reference like `cmSystemTools::ExpandLists` and
`cmSystemTools::ExpandListArgument`.
Motivation
----------
Since C++17 return value optimization is mandatory, so returning a
`std:vector<std::string>` from a function should be (at least) as fast as
passing a return vector reference to the function.
The new methods can replace `cmSystemTools::ExpandLists` and
`cmSystemTools::ExpandListArgument` in many cases, which leads to
shorter and simpler syntax.
E.g. the commonly used pattern
```
if (const char* value = X->GetProperty("A_KEY_STRING")) {
std::vector<std::string> valuesList;
cmSystemTools::ExpandListArgument(value, valuesList);
for (std::string const& i : valuesList) {
doSomething(i);
}
}
```
becomes
```
if (const char* value = X->GetProperty("A_KEY_STRING")) {
for (std::string const& i :
cmSystemTools::ExpandedListArgument(value)) {
doSomething(i);
}
}
```
On non-Windows platforms libuv assumes that file descriptors 0-2 are
always used for standard pipes and never for anything else. Otherwise,
libuv may re-use one of these descriptors and then fail an assertion
when closing it. Similarly, On Windows platforms our ConsoleBuf
implementation assumes that the standard handles are always open.
If CMake is run with any standard pipes closed, open them with
`/dev/null` or `NUL` to satisfy these assumptions.
Fixes: #19219
